TWI681929B - High purity silica sol and its production method - Google Patents

Abstract

An objective of this invention is to provide a production method for high purity silica sol which can use water glass as a raw material and has less metal impurity contents of Cu and Ni than conventional method.

The present invention provides a production method for high purity silica sol, which comprises the following steps [1] to [4] : [1] a step of ultrafiltrating an aqueous silica-alkali solution (a) to obtain a fine aqueous silica-alkali solution (b) ; [2] a step for obtaining a fine silica solution includes removing at least a part of cation included in the fine aqueous silica-alkali solution (b) by ion-exchanging method ; [3] a step for obtaining a high purity silica solution by use of chelating ion-exchange method for the fine silica solution ; [4]a step for obatining a high purity silica sol with both Cu concentration and Ni concentration in dry silicate are 50ppb or lower includes providing a part of the high purity silica solution as seed liquid, and the other as feeding liquid, adjusting the seed liquid to base and then being mixed with the feeding liquid.

Description

High-purity silica sol and manufacturing method thereof

The invention relates to high-purity silica sol and its manufacturing method.

In the past, a silica silica sol containing substantially no metallic impurities (Fe, Cr, Ni, Cu, etc.) was proposed. Such a high-purity silica sol can be suitably used as an abrasive for electronic materials such as semiconductor silicon wafers. If the above-mentioned metal impurities are contained in the silica sol, the metal impurities will diffuse into the wafer during the polishing process, deteriorating the wafer quality. Then the performance of the semiconductor device formed using such a wafer will be significantly reduced.

Examples of high-purity silica sols proposed in the past include those described in Patent Documents 1 to 3.

Patent Document 1 describes a method for producing colloidal silica, which is characterized by contacting an aqueous solution of silicate alkali with a cation exchange resin to prepare an active aqueous solution of silicic acid and contacting the aforementioned aqueous solution of active silicic acid with a chelating agent. The colloidal particles are grown, and then the silica impurities are removed while the silica is concentrated by ultrafiltration. Next, by such a manufacturing method, a colloidal silicon oxide having a Cu content per silicon oxide of 100 ppb or less or a Ni content per silicon oxide of 1000 ppb or less is obtained.

Patent Document 2 describes a manufacturing method containing the following steps: a step of preparing a solution of a strong acid or a salt of a strong acid in an aqueous solution of alkali metal silicate or active silicic acid; then a step of treating the solution with an ion exchange resin; then The step of preparing the silica sol by adding the solution obtained by the same procedure to the solution obtained by the ion exchange; then the step of treating the obtained silica sol with an ion exchange resin; further, the resulting silica The step of adding ammonia to the sol. Therefore, according to such a manufacturing method, colloidal silicon oxide having an average particle diameter in the range of 10 to 30 μm can be efficiently manufactured from alkali metal silicate containing polyvalent metal oxide containing impurities, and the SiO ₂ concentration is 30 to 50 It is a stable water-based silica sol with a weight% and a polyvalent metal oxide content other than silicon oxide of less than 300 ppm relative to silicon oxide.

Patent Document 3 describes a method for producing high-purity colloidal silica, which is characterized by the following steps: the first step of obtaining an aqueous silica solution by cation exchange treatment of water glass; adding acid and hydrogen peroxide to the resulting aqueous silica solution and adding The second step of the cation exchange treatment is performed again; the third step of mixing the silicon oxide aqueous solution obtained in the previous step with the ammoniacal alkali and oxidizing the colloidal silica. Therefore, by such a manufacturing method, very high-purity colloidal silicon oxide and high-purity synthetic quartz powder can be obtained, which is suitable for the grinding of silicon wafers, the bonding material of ceramic fibers, and the manufacture of Braun tube Various applications such as adhesives for phosphors and gelling agents for electrolytes in batteries.

[Prior Technical Literature] (Patent Literature)

Patent Document 1: Japanese Patent Laid-Open No. 2001-294417

Patent Document 2: Japanese Patent Laid-Open No. 6-16414

Patent Document 3: Japanese Patent Application Publication No. 2002-173314

However, it is hoped that there will be the development of high-purity silica sol with lower metal impurity content.

In addition, it was difficult to obtain high-purity silica sol from water glass in the past, but it is preferable to make it feasible.

The object of the present invention is to provide a method for manufacturing high-purity silica sol, which can use water glass as a raw material, and the Cu and Ni contents of metal impurities are lower than in the past. In addition, the object of the present invention is to provide a high-purity silica sol with low Cu and Ni content of metal impurities.

The inventor of the present invention has made a keen review to solve the above-mentioned problems, and completed the present invention. The present invention is the following (1) to (8).

(1) A method for manufacturing high-purity silica sol, which has the following steps [1] to [4]; [1] The step of ultrafiltration of an aqueous solution of silicate (a) and obtaining a purified aqueous solution of alkali silicate (b) [2] using the ion exchange method to remove at least a part of the cation components contained in the above-mentioned purified aqueous solution of alkaline silicate (b) to obtain purified silicate solution; [3] Use ions using chelating ion-exchange resin in the aforementioned refined silicic acid solution The exchange method to obtain a high-purity silicic acid solution; [4] Make part of the high-purity silicic acid solution as a seed liquid and the other part as a feed liquid. After adjusting to alkaline, mix with the above-mentioned supply solution to obtain a high-purity silica sol with a Cu concentration and Ni concentration of a dry amount of silica of 50 ppb or less.

(2) The method for producing a high-purity silica sol as described in (1) above, further comprising the following operations: adding an oxidizing agent to the aqueous solution (a) selected from the alkali silicate solution and the purified aqueous solution of the alkaline silicate (b) And at least one of the groups consisting of the aforementioned purified silicic acid solution.

(3) The method for producing high-purity silica sol as described in (2) above, wherein the oxidizing agent is hydrogen peroxide.

(4) The method for producing high-purity silica sol as described in any one of (1) to (3) above, wherein the step [3] is after adjusting the pH of the purified silicate solution to 2 or less, The step of obtaining the aforementioned high-purity silicic acid solution using the ion exchange method using chelating ion exchange resin.

(5) A high-purity silica sol with an average particle size of 2 to 300 nm, and the Cu concentration and Ni concentration of the dry amount of silica are below 50 ppb.

(6) The high-purity silica sol described in (5) above is obtained by the production method described in any one of (1) to (4) above.

(7) A polishing composition comprising the high-purity silica sol described in (5) or (6) above.

(8) The polishing composition as described in (7) above, contains at least one selected from the group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster, and a buffer.

According to the present invention, a method for producing high-purity silica sol can be provided, in which water glass can be used as a raw material, and the Cu and Ni contents of metal impurities are lower than in the past. In addition, the present invention can provide high-purity silica sol with low Cu and Ni content of metal impurities.

Next, the present invention will be described.

The present invention is a method for manufacturing high-purity silica sol, which has the following steps [1] to [4]; [1] The step of ultrafiltration of an aqueous silicate solution (a) to obtain a purified aqueous silicate solution (b) [2] using the ion exchange method to remove at least a part of the cation components contained in the above-mentioned purified aqueous solution of alkaline silicate (b) to obtain purified silicate solution; [3] In the above-mentioned refined silicic acid solution, an ion exchange method using chelating ion exchange resin is used to obtain a high-purity silicic acid solution; In the supply solution, the seed solution is adjusted to be alkaline and mixed with the supply solution to obtain a high-purity silica sol with a Cu concentration and a Ni concentration of the dry amount of silica of 50 ppb or less.

Hereinafter, the manufacturing method of such a high-purity silica sol is referred to as "the manufacturing method of the present invention".

In the manufacturing method of the present invention, it is preferable to have the following operation: add an oxidizing agent to a group selected from the group consisting of the aforementioned aqueous solution of silicate alkali (a), the aforementioned aqueous solution of purified silicate alkali (b), and the aforementioned purified silicate solution Of at least one of them.

In addition, in the production method of the present invention, the oxidizing agent is preferably hydrogen peroxide.

In addition, in the manufacturing method of the present invention, the step [3] preferably adjusts the pH of the purified silicic acid solution to 2 or less, and then uses the ion exchange method using a chelating ion exchange resin to obtain the high-purity silicic acid Liquid steps.

In addition, the present invention is a high-purity silica sol with an average particle size of 2 to 300 nm, and the Cu concentration and Ni concentration of the silica dry amount are both below 50 ppb.

Hereinafter, such a high-purity silica sol is referred to as "the silica sol of the present invention".

According to the manufacturing method of the present invention, the silica sol of the present invention can be obtained.

First, the manufacturing method of the present invention will be described.

<Step [1]>

The steps [1] possessed by the manufacturing method of the present invention will be described.

In step [1], first prepare an aqueous solution of silicate alkali (a) containing silicate alkali.

The aqueous solution of alkali silicate (a) is one in which sodium silicate, potassium silicate, lithium silicate and other silicate alkalis are dissolved in water. The alkali system here represents alkali metals (Li, Na, K, Rb, Cs, and Fr).

For the aqueous solution of alkali silicate (a), those who dissolve sodium silicate in water can also use water glass.

The concentration of SiO ₂ contained in the aqueous solution of alkali silicate (a) is not particularly limited, but it is preferably 15 to 30% by mass, more preferably 20 to 28% by mass, and still more preferably 22 to 26% by mass.

Here, the concentration of SiO ₂ contained in the aqueous solution of silicate alkali (a) is the result of adding hydrochloric acid and aqueous sodium hydroxide solution to neutralize the aqueous alkali silicate solution (a), adding potassium fluoride solution and titrating with hydrochloric acid. Obtained from the alkali component. In addition, specifically, the SiO ₂ concentration was measured according to the following reaction.

H ₂ SiO ₃ +6KF+H ₂ O → K ₂ SiF ₆ +4KOH

In addition, the concentration of alkali contained in the aqueous solution of alkali silicate (a) is, for example, in the case of an aqueous solution of sodium silicate, which is neutralized by adding hydrochloric acid to the aqueous solution of sodium silicate, and then added in excess, and back titrated with sodium hydroxide solution and Quantitative Na ₂ O. Measured in the same way as other alkalis.

The method for obtaining the aforementioned aqueous solution of silicate alkali (a) is not particularly limited. For example, it can be obtained by a conventionally known method. For example, it can be obtained by dissolving solid sodium silicate (sodium silicate glass shavings, etc.) in an aqueous solution of sodium hydroxide. For example, sodium silicate glass crumbs are dissolved in an aqueous sodium hydroxide solution for a sufficient time (for example, more than 30 minutes) at a high temperature (for example, 150° C. or higher) to obtain an aqueous solution of sodium silicate.

In addition, the aforementioned aqueous solution of silicate alkali (a) preferably has a molar concentration ratio of SiO ₂ to alkali oxide (SiO ₂ /alkaline oxide) of 1 to 7, more preferably 2 to 6, and even more preferably 2.5 to 5, and even better is 3.0 to 3.5. When the molar ratio is too low, the amount of alkali metal removed in the cation exchange step will increase, so it is less economical. In addition, when it is too high, the stability of the aqueous solution of silicate alkali (a) is low, so it is not practical.

In addition, as described below, it is preferable to add an oxidizing agent before ultrafiltration of the silicate alkali aqueous solution (a). The inventors found that at this time, the Cu concentration and Ni concentration in the high-purity silica sol obtained by the manufacturing method of the present invention would Become lower.

In addition, as the oxidizing agent, hydrogen peroxide, peracetic acid, urea peroxide, nitric acid, iodic acid (HIO ₃ ), ozone, etc. can be used, but hydrogen peroxide is preferably used.

In the case where an oxidizing agent is added to the above-mentioned purified aqueous solution of alkaline silicate (b) or the above-mentioned purified silicic acid solution described later, an oxidizing agent can also be used in the same manner, preferably hydrogen peroxide.

Here, regarding the dry amount of silicon oxide, the amount of the oxidizing agent added to the aqueous solution of alkali silicate (a) is preferably 0.001 to 20% by mass, more preferably 0.01 to 10% by mass.

In addition, the content of the dry amount of silicon oxide or the content of the dry amount of silicon oxide means that for the silicon oxide-containing substance (here, the aqueous solution of alkali silicate (a)), the object to be measured (here, the oxidant) is for SiO ₂ The value of the weight ratio of mass. In the following, in the present invention, the content of the dry amount of silicon oxide or the content of the dry amount of silicon oxide means this.

In step [1], such an aqueous solution of silicate alkali (a) is ultrafiltered.

Ultrafiltration can be performed using conventionally known ultrafiltration membranes. The molecular weight cut off of the ultrafiltration membrane is preferably 100 to 10,000, more preferably 1000 to 9000, and still more preferably 3000 to 6000.

By performing such ultrafiltration, a refined aqueous solution of silicate alkali (b) can be obtained.

The concentration of SiO ₂ contained in the obtained purified aqueous alkali silicate solution (b) is preferably 15 to 30% by mass, more preferably 20 to 28% by mass, and still more preferably 20 to 26% by mass.

In addition, the concentration of SiO ₂ contained in the purified aqueous solution of alkali silicate (b) is obtained in the same manner as the concentration of SiO ₂ contained in the aqueous solution of alkali silicate (a).

In addition, it is preferable to add an oxidizing agent to the purified aqueous solution of alkali silicate (b). The inventors found that the concentration of Cu and Ni in the high-purity silica sol obtained by the manufacturing method of the present invention becomes lower at this time.

Here, relative to the dry amount of silicon oxide, the amount of the oxidizing agent added to the above-mentioned purified aqueous solution of alkali silicate (b) is preferably 0.001 to 20% by mass, more preferably 0.01 to 10% by mass.

<Step [2]>

The steps [2] of the manufacturing method of the present invention will be described.

In the step [2], at least a part of the cation component contained in the purified aqueous alkaline silicate solution (b) is removed by using the ion exchange method in the purified aqueous alkaline silicate solution (b).

The ion exchange method is not particularly limited, and for example, a conventionally known method can be used. For example, a method using a cation exchange resin can be mentioned.

Through this step [2], a purified silicic acid solution that removes at least a part of the cationic component (usually to remove most of the cationic component) can be obtained.

The concentration of SiO ₂ contained in the resulting purified silicic acid solution is preferably 1 to 15% by mass, more preferably 1 to 10% by mass, and still more preferably 2 to 8% by mass.

In addition, the total amount of ignition residue (solid residue) of the refined silicic acid solution fired at 1000°C for 1 hour is taken as SiO ₂ , and the calculated value based on the mass is included in the refined silicic acid solution SiO ₂ concentration.

<Step [3]>

The steps [3] of the manufacturing method of the present invention will be described.

In step [3], the ion exchange method using chelating ion exchange resin is used for the above-mentioned purified silicic acid solution.

The inventor of the present invention has keenly reviewed and found that by performing ultrafiltration in step [1] and ion exchange using a chelating ion exchange resin in step [3], an oxide silica sol with extremely low Cu concentration and Ni concentration can be obtained.

In the chelated ion exchange resin, the above-mentioned purified silicic acid solution is preferably passed at a space velocity of about 0.5 to 10 h ^-1 , more preferably about 1.5 to 5.0 h ^-1 , and still more preferably about 2 to 4 h ^-1 .

In addition, in step [3], it is preferable to use an ion exchange method using a chelating ion exchange resin after adding an oxidizing agent to the purified silicate solution. The inventors found that the concentration of Cu and Ni in the high-purity silica sol obtained by the manufacturing method of the present invention becomes lower at this time.

Here, relative to the dry amount of silicon oxide, the amount of the oxidizing agent added to the above-mentioned purified silicic acid solution is preferably 0.001 to 20% by mass, more preferably 0.01 to 10% by mass.

In addition, in step [3], it is preferable to use an ion exchange method using a chelating ion exchange resin after adjusting the pH of the purified silicate solution to 2 or less (preferably 1 to 2). The inventors found that the concentration of Cu and Ni in the high-purity silica sol obtained by the manufacturing method of the present invention becomes lower at this time.

In addition, in step [3], it is preferable to adjust the pH to 2 or less after adding an oxidizing agent (preferably hydrogen peroxide) to the above-mentioned purified silicic acid solution, and then use an ion exchange method using a chelating ion exchange resin. The inventors found that the concentration of Cu and Ni in the high-purity silica sol obtained by the manufacturing method of the present invention becomes lower at this time.

Here, relative to the dry amount of silicon oxide, the oxygen in the aforementioned purified silicic acid solution The amount of the chemical agent added is preferably 0.001 to 20% by mass, more preferably 0.01 to 10% by mass.

In addition, the means for adjusting the pH of the purified silicic acid solution to 2 or less (preferably 1 to 2) is not particularly limited, and can be adjusted by adding a conventionally known acid (hydrochloric acid or the like).

Through this step [3], high purity silicic acid solution can be obtained.

<Step [4]>

The steps of the manufacturing method of the present invention [4] will be described.

In step [4], a part of the high-purity silicic acid solution is used as a seed solution, and the other part is used as a supply solution. The seed solution is adjusted to be alkaline and mixed with the supply solution.

After using a part of the aforementioned high-purity silicic acid liquid as a seed liquid, an alkali can be added to the seed liquid to adjust the solution to be alkaline. Specifically, after adjusting the pH to 10 to 13 (preferably 11 to 12), one side is kept at preferably 20 to 98°C (more preferably 50 to 95°C, still more preferably 80 to 90°C) ) While adding the aforementioned supply liquid, it can be mixed with the supply liquid.

Here, the supply liquid is preferably added to the seed liquid at 1 to 30°C, more preferably at 1 to 20°C.

It is preferable to slowly add the supply liquid to the seed liquid whose pH and temperature are adjusted as described above, so that the silicon oxide fine particles will grow in the seed liquid to obtain the silica sol.

After the feed liquid is added to the seed liquid, if it is kept at a high temperature (approximately 80 to 90° C.) for several hours, the silicon oxide fine particles tend to grow, which is preferable.

Through this step [4], relative to the dry amount of silicon oxide, Cu The concentration (mass concentration) and Ni concentration (mass concentration) are both high-purity silica sols below 50 ppb.

Here, the Cu concentration and Ni concentration of the dry amount of silicon oxide are preferably as low as those of the silica sol of the present invention described later. In addition, it is preferable to have the same average particle diameter as the silica sol of the present invention described later.

The SiO ₂ concentration (mass %) in the high-purity silica sol is to add sulfuric acid to the high-purity silica sol and evaporate to dryness, then ignite and determine the mass. Then, after adding sulfuric acid and hydrofluoric acid together, it was evaporated to dryness and the mass was measured. The mass reduction at this time was determined by silicon oxide (SiO ₂ ).

In addition, the concentration of Cu and Ni in the high-purity silica sol is that after adding nitric acid and hydrofluoric acid to the silica sol and heating it, it evaporates to dryness and then adds nitric acid and water and dissolves by heating, adding water and diluting to a certain amount , Quantify the value using a graphite atomic absorption meter.

After the SiO ₂ concentration, Cu concentration, and Ni concentration are determined in this manner, the Cu concentration and Ni concentration of the silicon oxide dry amount are determined from the ratio of Cu concentration or Ni concentration to the SiO ₂ concentration.

Next, the silica silica sol of the present invention will be explained.

The average particle diameter of the silica fine particles contained in the silica sol of the present invention is 2 to 300 nm, preferably 5 to 100 nm, and more preferably 10 to 80 nm.

Here, the average particle diameter of the silica fine particles represents the value measured by the Sears method.

The Siers method is a method performed in the order of 1) to 6) below.

1) Take a sample equivalent to 1.5g of SiO ₂ and place it in a beaker, move to a constant temperature reaction tank at 25°C, add pure water to make the liquid volume 90ml. The following operations are performed in a constant temperature reaction tank maintained at 25°C.

2) Add 0.1 mol/L hydrochloric acid aqueous solution so that the pH becomes 3.6.

3) Add 30g of sodium chloride, dilute to 150ml with pure water and stir for 10 minutes.

4) The pH electrode was set, and 0.1 mol/L sodium hydroxide aqueous solution was dropped into it while stirring to adjust the pH to 4.0.

5) Titrate the sample adjusted to pH 4.0 with 0.1 mol/L sodium hydroxide aqueous solution, record the titration and pH value in the range of pH 8.7 to 9.3 above 4 points, set 0.1 mol/L sodium hydroxide aqueous solution The titration amount is X, and the pH value at this time is Y, and a calibration curve is prepared.

6) The consumption V (ml) of 0.1 mol/L sodium hydroxide aqueous solution required for each 1.5 g of SiO ₂ from pH 4.0 to 9.0 is obtained by the following formula (3), and is obtained by the following formula (4) Calculate the specific surface area. In addition, the average particle diameter D1 (nm) is determined from the formula (5).

V=(A×f×100×1.5)/(W×C)‧‧‧‧(3)

SA1=29.0V-28‧‧‧‧(4)

D1=6000/(ρ×SA1)‧‧‧‧(5)(ρ: density of sample)

The meaning represented by the symbol in the above formula (3) is as follows.

A: The titration amount (ml) of 0.1 mol/L sodium hydroxide solution required from pH 4.0 to 9.0 per 1.5 g of SiO ₂

f: 0.1 mol/L sodium hydroxide solution titer

C: SiO ₂ concentration of sample (%)

W: amount of sample taken (g)

The silica sol of the present invention is the Cu concentration (quality) of the dry amount of silica The concentration) is 50 ppb or less, preferably 40 ppb or less, more preferably 30 ppb or less, still more preferably 20 ppb or less, and still more preferably 10 ppb or less.

In addition, the silica concentration of the silica sol-based silica of the present invention is 50 ppb or less, preferably 40 ppb or less, more preferably 30 ppb or less, even more preferably 20 ppb or less, and even more preferably 10 ppb or less. .

In addition, the silica sol of the present invention preferably contains substantially no carbon. That is, the carbon content in the silica sol of the present invention is preferably 0.5% by mass or less. The carbon content is more preferably 0.3% by mass or less, and still more preferably 0.1% by mass or less.

Here, the carbon content of the silica sol of the present invention is obtained by burning the silica sol in a high-frequency furnace of a carbon/sulfur analyzer, and detecting CO and CO _{2 of the} combustion product by infrared absorption.

In addition, the SiO ₂ concentration, Cu concentration, and Ni concentration contained in the silica sol of the present invention mean the same as the SiO ₂ concentration, Cu concentration, and Cu concentration contained in the high-purity silica sol obtained by the aforementioned manufacturing method of the present invention. The value measured by Ni concentration.

The silica sol of the present invention contains silica fine particles having the above average particle diameter, and is a high purity silica sol having the above Cu concentration and Ni concentration.

The dispersion medium in the silica sol of the present invention is not particularly limited, and is preferably an aqueous system, more preferably water.

In addition, the solid content concentration in the silica sol of the present invention is not particularly limited, but it is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, and still more preferably 20 to 40% by mass.

In addition, the pH in the silica sol of the present invention is not particularly limited, but it is preferably 8 to 12, and more preferably 9 to 11.

The silica sol of the present invention may contain conventionally known stabilizers such as HCl or NaOH.

The production method of the silica sol of the present invention is not particularly limited, but it can be produced by the production method of the present invention.

The silica sol of the present invention can be suitably used as an abrasive.

The polishing composition containing the silica sol of the present invention has a lower concentration of Ni and Cu than in the past, so it can be suitably used as a polishing agent for electronic materials such as semiconductor silicon wafers.

The polishing composition preferably contains at least one selected from the group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster, and a buffer.

(Example) <Example 1> [Purification of aqueous solution of sodium silicate]

Prepare a sodium silicate aqueous solution (referred to as ``water glass'' with an SiO ₂ concentration of 24.06 mass%, a Na ₂ O concentration of 7.97 mass%, a Cu concentration (dry amount of silicon oxide) of 460 ppb, and a Ni concentration (dry amount of silicon oxide) of 640 ppb. A"). In addition, the SiO ₂ concentration, Na ₂ O concentration, Cu concentration, and Ni concentration were measured by the aforementioned method.

Next, the sodium silicate aqueous solution was filtered using an ultrafiltration membrane (SEP-1013 manufactured by Asahi Kasei Chemicals Co., Ltd., molecular weight cut-off of 3000) to obtain a purified aqueous alkaline silicate solution (b) of filtered water.

When the SiO ₂ concentration of the purified aqueous solution of alkaline silicate (b) was measured by the aforementioned method, the result was 23.2% by mass.

[Adjustment of refined silicic acid solution]

Pure water was added to 3880 g of the obtained purified alkaline silicate aqueous solution (b) to make the SiO ₂ concentration 5.0% by mass.

Then 5.0% by mass of purified silicon obtained from an aqueous solution of alkali (b) 18kg, a space velocity of 3.0h ^-1 allowed to flow through a strongly acidic cation exchange resin of 6L (SK1BH, manufactured by Mitsubishi Chemical Corporation) to give a pH of 2.7 18kg of refined silicic acid solution.

When the SiO ₂ concentration in the obtained purified silicic acid liquid was measured by the method described above, it was 4.7% by mass.

[Adjustment of High Purity Silicic Acid Solution]

Next, 160 g of 3.0% by mass of hydrogen peroxide (0.56% by mass relative to the dry amount of silica) was added to 18 kg of purified silicic acid solution, and 1% by mass of hydrochloric acid was added to adjust the pH to 2. Then, the solution was passed through a chelating ion exchange resin (CR-11, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h ^-1 to obtain a high-purity silicic acid solution with a pH of 2.0.

The SiO ₂ concentration of the obtained high-purity silicic acid liquid was 4.5% by mass.

[Manufacture of high purity silica sol]

A part (414.4 g) of the high-purity silicic acid liquid obtained as described above was taken out as a seed liquid, and the other part (10.63 kg) of the high-purity silicic acid liquid was taken out as a supply liquid.

Next, 191.1 g of a 5 mass% potassium hydroxide aqueous solution was added to 725.8 g of pure water, and the seed liquid was further added and heated. Next, after reaching 83℃ For 30 minutes, while maintaining the temperature, it took 11 hours at a constant rate to add the supply liquid to it. Next, after the whole amount of the supply liquid was added to the seed liquid, it was kept at 83°C and heated for 1 hour, and cooled to room temperature to obtain an silica sol. This silica sol was concentrated to 12% by mass using an ultrafiltration membrane (SIP-1013) manufactured by Asahi Kasei Chemicals Co., Ltd., and then concentrated to 30% by mass using a rotary evaporator to obtain a high-purity silica sol.

Next, when the average particle diameter of the obtained high-purity silica sol was measured by the Siers method, the result was 17.8 nm.

In addition, the Cu concentration (dry amount of silica) and Ni concentration (dry amount of silica) in the obtained high-purity silica sol were measured by the aforementioned method. As a result, the Cu concentration (dry amount of silicon oxide) did not reach 1 ppb, and the Ni concentration (dry amount of silicon oxide) was 7 ppb.

<Example 2>

In Example 1, an ultrafiltration membrane (SEP-1013, molecular weight cutoff 3000) was used to filter the sodium silicate aqueous solution to obtain a purified aqueous solution of alkali silicate (b), but in Example 2, an ultrafiltration membrane (Asahi Kasei) was used Manufactured by CHEMICALS, SIP-1013, molecular weight cutoff 6000) The same sodium silicate aqueous solution is filtered to obtain a purified aqueous solution of alkaline silicate (b).

In addition, in Example 1, hydrogen peroxide was added to the purified silicic acid solution, hydrochloric acid was added to adjust the pH to 2, and the solution was passed through the chelating ion exchange resin. However, in Example 2, hydrogen peroxide was not added nor added. The pH adjustment operation of hydrochloric acid. Next, the refined silicic acid solution was passed through the same chelated ion exchange resin at the same spatial velocity to obtain a high-purity silicic acid solution with a pH of 2.7. When the SiO ₂ concentration in the obtained high-purity silicic acid liquid was measured by the aforementioned method, the result was 4.5% by mass.

Next, otherwise, the same operation and the same measurement as in Example 1 were performed.

As a result, the average particle size of the obtained high-purity silica sol was 17.8 nm, the Cu concentration (dry amount of silica) was 30 ppb, and the Ni concentration (dry amount of silica) was 20 ppb.

<Example 3>

Use a sodium silicate aqueous solution (referred to as ``water glass'') with a SiO ₂ concentration of 24.64% by mass, a Na ₂ O concentration of 8.08% by mass, a Cu concentration (dry amount of silicon oxide) of 690 ppb, and a Ni concentration (dry amount of silicon oxide) of 240 ppb. B") replaces the water glass A used in Example 1.

Next, otherwise, the same operation and the same measurement as in Example 1 were performed.

As a result, the average particle size of the obtained high-purity silica sol was 17.6 nm, the Cu concentration (dry amount of silica) was 24 ppb, and the Ni concentration (dry amount of silica) was 9 ppb.

<Example 4>

Use a sodium silicate aqueous solution (referred to as ``water glass'' with a SiO ₂ concentration of 24.43% by mass, a Na ₂ O concentration of 7.40% by mass, a Cu concentration (dry amount of silicon oxide) of 450 ppb, and a Ni concentration (dry amount of silicon oxide) of 160 ppb. C") replaces the water glass A used in Example 1.

Next, otherwise, the same operation and the same measurement as in Example 1 were performed.

As a result, the average particle size of the obtained high-purity silica sol was 17.6 nm, The Cu concentration (dry amount of silicon oxide) is 23 ppb, and the Ni concentration (dry amount of silicon oxide) is less than 1 ppb.

<Example 5>

To 5 kg of water glass B, add 232.8 g of 3.0% by mass of hydrogen peroxide (the dry amount of silica is 0.567% by mass), and stir thoroughly.

Next, the obtained sodium silicate aqueous solution after adding hydrogen peroxide was filtered using an ultrafiltration membrane (SIP-1013, molecular weight cutoff 6000) to obtain a purified aqueous alkaline silicate solution (b) of filtered water.

Next, pure water was added to the obtained purified alkaline silicate aqueous solution (b) so that the SiO ₂ concentration was 5.0% by mass. Subsequently, the resulting purified silicon of 5.0% by mass aqueous solution of alkali (B), a space velocity of 3.0h ^-1 allowed to flow through a strongly acidic cation exchange resin of 6L (SK1BH, manufactured by Mitsubishi Chemical Corporation), was purified to give a pH of 2.7 Silicic acid.

Next, the purified silicic acid solution was passed through the chelating ion exchange resin (CR-11, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h ^-1 to obtain a high-purity silicic acid solution with a pH of 2.7. When the SiO ₂ concentration in the obtained high-purity silicic acid liquid was measured by the method described above, the result was 4.5% by mass.

Next, in the same manner as in Example 1, 191.1 g of a 5 mass% potassium hydroxide aqueous solution was added to pure water, and a seed liquid was added and heated. Then, after reaching 83° C. for 30 minutes, while maintaining the temperature, It took 11 hours to add the supply liquid to it at a certain speed. Next, after the whole amount of the supply liquid was added to the seed liquid, it was kept at 83°C and heated for 1 hour to obtain a high-purity silica sol.

Next, the same measurement as in Example 1 was performed.

As a result, the average particle size of the obtained high-purity silica sol was 17.6 nm, the Cu concentration (dry amount of silica) was 5 ppb, and the Ni concentration (dry amount of silica) was less than 1 ppb.

<Comparative Example 1>

Pure water was added to the water glass A used in Example 1 to make the SiO ₂ concentration 5.0% by mass.

Subsequently, the resulting silicon of 5.0 mass% aqueous solution of sodium 18kg a space velocity of 3.0h ^-1 allowed to flow through a strongly acidic cation exchange resin of 6L (SK1BH, manufactured by Mitsubishi Chemical Corporation), to give silicate solution 18kg.

When the SiO ₂ concentration in the obtained silicic acid solution was measured by the aforementioned method, the result was 4.7% by mass. The silicic acid solution was diluted with pure water to 4.5% by mass.

Next, a part (414.4 g) of the silicic acid liquid thus obtained was taken out as a seed liquid, and the other part (10.63 kg) of the silicic acid liquid was taken out as a supply liquid.

Next, in the same manner as in Example 1, 191.1 g of a 5 mass% potassium hydroxide aqueous solution was added to pure water, and a seed liquid was further added and heated. After holding for 30 minutes, while maintaining the temperature, it took 11 hours to add the supply liquid to it at a certain speed. Next, after the whole amount of the supply liquid was added to the seed liquid, it was kept at 83° C. and heated for 1 hour to obtain a silica sol.

Next, the same measurement as in Example 1 was performed.

As a result, the average particle size of the obtained high-purity silica sol was 17.6 nm, the Cu concentration (dry amount of silica) was 235 ppb, and the Ni concentration (dry amount of silica) was 610 ppb.

<Comparative Example 2>

Pure water was added to the water glass A used in Example 1 to make the SiO ₂ concentration 5.0% by mass.

Next, 18 kg of the obtained 5.0% by mass sodium silicate aqueous solution was passed through a 6 L strong acid cation exchange resin (SK1BH, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h ^-1 to obtain 18 kg of silicate solution. When the SiO ₂ concentration in the obtained silicic acid solution was measured by the aforementioned method, the result was 4.7% by mass.

Next, 18 kg of silicic acid solution was passed through a chelating ion exchange resin (CR-11, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h ^-1 to obtain a chelating resin ion exchange silicic acid solution having a pH of 2.7. The SiO ₂ concentration is 4.5% by mass.

Next, a part (414.4 g) of the chelating resin ion exchange silicic acid liquid thus obtained was taken out as a seed liquid, and the other part (10.63 kg) of the chelating resin ion exchange silicic acid liquid was taken out as a supply liquid.

Next, in the same manner as in Example 1, 191.1 g of a 5 mass% potassium hydroxide aqueous solution was added to pure water, and a seed liquid was further added and heated. After holding for 30 minutes, while maintaining the temperature, it took 11 hours to add the supply liquid to it at a certain speed. Next, after the whole amount of the supply liquid was added to the seed liquid, it was kept at 83° C. and heated for 1 hour to obtain a silica sol.

Next, the same measurement as in Example 1 was performed.

As a result, the average particle size of the obtained high-purity silica sol was 17.7 nm, the Cu concentration (dry amount of silica) was 80 ppb, and the Ni concentration (dry amount of silica) was 150 ppb.

<Comparative Example 3>

Except that water glass B was used instead of water glass A, the same operation as in Comparative Example 2 was performed, and the same measurement was performed.

As a result, the average particle diameter of the obtained silica sol was 17.8 nm, and the Cu concentration (The dry amount of silicon oxide) is 105 ppb, and the Ni concentration (dry amount of silicon oxide) is 187 ppb.

<Comparative Example 4>

Except that water glass C was used instead of water glass A, the same operation as in Comparative Example 2 was performed, and the same measurement was performed.

As a result, the average particle diameter of the obtained silica sol was 17.6 nm, the Cu concentration (dry amount of silica) was 113 ppb, and the Ni concentration (dry amount of silica) was 97 ppb.

In Examples 1 to 5, the operation of filtering the aqueous solution of sodium silicate using an ultrafiltration membrane was performed, and the operation of passing the refined silicic acid solution through chelating ion exchange resin was repeated. In the high-purity silica sol obtained in Examples 1 to 5, the Cu concentration and Ni concentration of the dry amount of silica are below 50 ppb. Specifically, the Cu concentration of the dry amount of silicon oxide is 30 ppb or less, and the Ni concentration of the dry amount of silicon oxide is 20 ppb or less.

In addition, in Example 1, an operation of filtering an aqueous solution of sodium silicate using an ultrafiltration membrane was performed, hydrogen peroxide was added to the purified silicic acid solution, and hydrochloric acid was added to adjust the pH to 2, and then the operation of passing the liquid through chelating ion exchange resin was performed. In the high-purity silica sol obtained in Example 1, the Cu concentration and Ni concentration of the silica dry amount will be lower, specifically, both are below 10 ppb.

In addition, in Example 5, hydrogen peroxide was added to the sodium silicate aqueous solution, and then the operation of filtering with an ultrafiltration membrane was performed, and the operation of passing the liquid through chelating ion exchange resin was performed. In the high-purity silica sol obtained in Example 5, the Cu concentration and Ni concentration of the silica dry amount will be lower, specifically, both are below 5 ppb.

In contrast, the silica sol obtained in Comparative Examples 1 to 4 has a Cu concentration of 80 to 235 ppb in the dry amount of silica and a Ni concentration of 97 to 610 ppb in the dry amount of silica.

Claims (5)

A method for manufacturing high-purity silica sol, having the following steps [1] to [4]; [1] The step of ultrafiltration of an aqueous solution of silicate alkali (a) to obtain a purified aqueous solution of alkali silicate (b); [2 ] The step of obtaining a purified silicic acid solution by removing at least a part of the cation components contained in the purified aqueous solution of alkaline silicate (b) using ion exchange method in the purified aqueous solution of alkaline silicate (b); [3] In the aforementioned purification For the silicic acid solution, an ion exchange method using chelating ion exchange resin is used to obtain a high-purity silicic acid solution; [4] a part of the high-purity silicic acid solution is used as a seed liquid, and the other part As a feed liquid, the seed liquid is adjusted to an alkaline pH of 10 to 13 and mixed with the feed liquid to obtain a high-purity silica sol having a Cu concentration and a Ni concentration of 50 ppb or less for the dry amount of silica Steps. The method for producing high-purity silica sol as described in item 1 of the patent application scope, wherein the step [3] is to adjust the pH of the purified silicate solution to 2 or less, and then use ions using chelating ion exchange resin Exchange method to obtain the aforementioned high-purity silicic acid solution. A high-purity silica sol with an average particle size of 2 to 300 nm. The Cu concentration and Ni concentration of the silica dry amount are both below 10 ppb. A polishing composition containing high-purity silica sol as described in item 3 of the patent application. The polishing composition as described in item 4 of the patent application scope contains At least one selected from the group consisting of grinding accelerators, surfactants, heterocyclic compounds, pH adjusting agents, and buffering agents.